Feedback Needed - Homebuilt Aircraft Cruise Speeds

[rwanttaja]

Looking at the graphic, it strikes me kind of funny that folks stall on takeoff, and though I know of one fatal wreck that happened that way (test flight #1 in a Nieuport 11 replica), I am trying to figure it out.

Best I can reckon is that apart from test phase fun with engines, it's short fields doing the pilot no favors as he goes for too much max climb to clear obstacles that has to be to blame.

I haven't attempted to split this out any further. But I'd guess pilot inattention is probably more a factor.

We're continually warned about stalling on the base-to-final turn, and many of us a quivering masses of concentration as we prepare to land. Flying with the power off is a multisensory endeavor, especially with an open-cockpit wire-braced airplane like a Nieuport. You've got the gauge, you've got your ears, and you've got the air rushing by.

But takeoff? Meh. Once the wheels come off the ground, we relax. The engine is the overriding physical and audio feature, and if it's running strong, there's little other physical phenomenae that might warn you the plane is getting slow. You're pulling out your charts, you're planning your turn onto course, you're watching the other planes trying to enter the pattern. The engine's running...who's going to worry?

Any enlightenment?

Enlightenment? Next time you hit a food cart, ask for a Zen hot dog: "Make me one with everything."

Ron Wanttaja

[Ron Blum]

There are a lot of reasons why the stall-spin accident rate is much higher on takeoff/go-around than on landing. Yes, this surprised me when I first heard it, too, but ...

Landing:
1. Initial, target airspeed is 30% above stall speed.
2. Power is low --> therefore little requirement for a rudder input.
3. Airplane is allowed to descend --> therefore, although bank angle may be higher, G-load may not be raised correspondingly.

Takeoff:
1. Initial, target airspeed is only 20% above stall speed.
2. Power is high --> therefore rudder is required to properly coordinate.
3. Airplane is NOT allowed to descend --> therefore any bank angle will increase the G-load
4. Typical pilot reaction to upcoming terrain is to pull back on the control --> increasing G-load and decreasing airspeed.
5. Engine failure with pilots that fail to lower the nose to maintain airspeed.
6. Configuration (power) changes on go-around that cause the nose to go up. The pitch rate may be such that the stall warning is not early enough to warn the pilot that the airplane is going to depart.

AOPA did a great report on stall-spin accidents between 2000-2016 (published during OSH17). I would say that the link is below, but it looks like it didn't paste correctly. If cutting and pasting the address below doesn't work, just Google "AOPA Keep the Wings Flying", and it will come up.

https://www.aopa.org/-/media/files/a...spin.pdf?la=en

Hope this "enlightens" a little; it has for me. This is giving me (and others, too?) sparks to hopefully find potential solutions.

[rwanttaja]

Along these lines, I'd also like some feedback/suggestions as to terminology.

As part of the stall study, I'm looking how often the pilots of specific homebuilt types accidentally stall as part of the accident sequence. I've got it broken down into two basic categories: Stalls that occur out of normal operation, and stalls that happen during the forced landing subsequent to an engine failure.

I think it's an important distinction. Once the engine fails, the pilots are under a tremendous strain, and often the stalls occur out of the unconscious desire to avoid ground contact. On the other hand, a stall that occurs during normal flight might indicate an aircraft design that doesn't provide enough warning, or presents a more difficult recovery.

I'm looking for some nice terminology for those two conditions. Right now, I'm using "Inadvertent Stall" for the cases where there is not a power issue. Might use, "Force-landing stall" for the emergency cases. Trouble is, the stalls during forced landings are "Inadvertent Stalls" as well.

Anybody have some good suggestions?

And just to tease (Spoiler alert): The out of 15 common homebuilt aircraft, the two scoring the best in the "Inadvertent Stall" category are designs that were eventually type certificated under Normal category (with minor changes)....

Ron Wanttaja

[Ron Blum]

This is exactly where a couple of us are trying to take the ASTM committee. By educated guess, all stalls are inadvertent, except those performed >3,000 ft AGL. for training/practice. We are looking at stalls due to primary control inputs, configuration changes (such as flaps), engine failure, power changes, etc.

As you have eluded to, the stall may not be a single event but rather a chain of events that terminated in a stall.

Thanks for the great work!

[Bill Berson]

The "moose turn stall" is named for the situation where a pilot is doing several low and slow circles perhaps with flaps. The airplane gradually gets behind the power curve and can't climb in a turn. But instead of rolling wings level first the pilot instead pulls the stick back and stalls in the turn at 100 feet agl.

[dougbush]

As part of the stall study, I'm looking how often the pilots of specific homebuilt types accidentally stall as part of the accident sequence. I've got it broken down into two basic categories: Stalls that occur out of normal operation, and stalls that happen during the forced landing subsequent to an engine failure.

I think it's an important distinction.

I'm not sure there's a distinction to be made. An engine failure is a dramatic distraction, but if one doesn't understand angle of attack, any distraction will do. I suspect those other inadvertent stalls are precipitated by some lesser distraction.

An unintentional stall says more about pilot training and/or testing than about aircraft design. Anyway, there's a more direct method to evaluate a design: have it test-flown by someone with experience in a variety of aircraft and ask whether it did anything weird.

Different types of planes appeal to different types of pilots, which could account for some variation in frequency of stall accidents. I don't think it's fair to blame the designer for the faults of the pilots who like it.

[Ron Blum]

[QUOTE=dougbush;69943 I don't think it's fair to blame the designer for the faults of the pilots who like it.[/QUOTE]

I would agree that a stall after an engine failure is poor training. Look at the glider world. Gliders have a lot of engine failures (rope breaks) on takeoff. They are taught to think of what to do if the rope breaks on takeoff at different altitudes and with different runway lengths and surrounding terrain. I think the powered world could learn from their example.

Not blaming designers or pilots, I believe that many real world stall scenarios are not addressed by the current regulations. For a couple examples, at what airspeed will full aileron input cause the airplane to depart? And, how long does an inattentive pilot get to react to a stall warning on a go around in an airplane that pitches up abruptly when adding full power in the landing configuration? Both of these are not tested by the regulations.

it’s not who we can blame, but rather what can be accomplished so that we can greatly reduce the number of these fatal accidents.

[Frank Giger]

Ron, there are some things I am not going to test in my aircraft.

[Ron Blum]

Ron, there are some things I am not going to test in my aircraft.

Frank: I agree with you from an E-AB standpoint. From a certificated aircraft standpoint, I think that we (OEMs) should test as much as is reasonable. These organizations know how to approach high-risk testing and have the safety/recovery equipment (spin chute, personal chutes, telemetry, etc.) to do these tests safely. If we learn something there, it can be passed along to the E-AB world. (yes, all airplanes are different). OR ... (and this is where the certification world is most likely going to go)

Stick pushers (or some form of stall barrier system) will become standard on all airplanes. For an OEM it’s easier, cheaper and eliminates an unknown quantity in the flight test program... and the >$2M spin program.

(it is my strong belief that...) Nobody intentionality stalls an airplane at low altitude. Yet the number 1 cause of fatal accidents year after year is pilots controlling the aircraft into a stall. Regretfully, what the NTSB labels “maneuvering” stalls is a large percentage of the accidents.

We, as an aviation community, need to come up with ideas on how to break that fatal chain before the pilot gets to that point.

[CarlOrton]

OK; 49 comments thus far, and only a handful provided data to Ron's original request. My Sonex did 133 mph WOT at 2500'. I usually cruised more at 116 mph for economy, quieter, etc.

I'd like to see the comprehensive data, by model, at some point.